Follow-up study to evaluate the sustained clinical efficacy of ragweed MATA MPL (allergy therapeutics) in patients with ragweed-induced seasonal allergic rhinitis upon re-exposure to ragweed pollen in an environmental exposure chamber (EEC) model, approximately one year after pre-seasonal treatment in 2005

Ragweed MATAMPL has been developed to provide pre-seasonal specific immunotherapy for patients with hypersensitivity to ragweed pollen (hay fever). This novel formulation is designed to provide a vaccine that will be efficacious with only four escalating dose injections administered before the start of the pollen season. In this Follow-up Study the Efficacy will be assessed by exposing allergic subjects to Ragweed pollen in an environmental exposure chamber EEC. Patient symptomatic response to pollen and patient quality of life in the EEC will be determined. Patients who previously completed two EEC portions of study Ragweed MATAMPL 204 and who had been treated with either Ragweed MATA MPL or Placebo before the 2005 ragweed season will be enrolled.